Desmodesmus Sp Research Articles

Acid-adapted microalgae exhibit phenotypic changes for their survival in acid mine drainage samples.

Phenotypic plasticity or genetic adaptation in an organism provides phenotypic changes when exposed to the extreme environmental conditions. The resultant physiological and metabolic changes greatly enhance the organism's potential for its survival in such harsh environments. In the present novel approach, we tested the hypothesis whether acid-adapted microalgae, initially isolated from non-acidophilic environments, can survive and grow in acid-mine-drainage (AMD) samples. Two acid-adapted microalgal strains, Desmodesmus sp. MAS1 and Heterochlorella sp. MAS3, were tested individually or in combination (co-culture) for phenotypic changes during their growth in samples collected from AMD. The acid-adapted microalgae in AMD exhibited a two-fold increase in growth when compared with those grown at pH 3.5 in BBM up to 48h and then declined. Furthermore, oxidative stress triggered several alterations such as increased cell size, granularity, and enhanced lipid accumulation in AMD-grown microalgae. Especially, the apparent limitation of phosphate in AMD inhibited the uptake of copper and iron in the cultures. Interestingly, growth of the acid-adapted microalgae in AMD downregulated amino acid metabolic pathways as a survival mechanism. This study demonstrates for the first time that acid-adapted microalgae can survive under extreme environmental conditions as exist in AMD by effecting significant phenotypic changes.

Development of bioplastics from a microalgae consortium from wastewater

Nowadays, as the world population is in need of creating alternative materials that can replace conventional plastics, microalgae biomass may be identified as a viable source for producing more environmentally friendly materials. Scenedesmus sp and Desmodesmus sp are the main components (~80%) of a microalgae consortium (MC) that first has been used to remove Nitrogen and Phosphorus from wastewater. The potential to develop bioplastic materials from MC considering its relatively high protein content (~48%) has been assessed in the present manuscript, using as a reference a commercial biomass rich an Arthrospira specie (AM) also present in the studied consortium.Bioplastics were obtained through injection moulding of blends obtained after mixing with different amounts of glycerol, and eventually characterized using Dynamic Mechanical Thermal Analysis (DMTA), water immersion and tensile tests. All bioplastics displayed a glass transition temperature around 60 °C, showing a thermoplastic behavior which is less pronounced in the CM based bioplastics. This would imply a greater thermal resistance of bioplastics produced from the biomass harvested in wastewater. Moreover, these bioplastics showed a lower ability to absorb water when immersed, due to the lower deformability displayed in the tensile tests. The mechanical properties of all samples, independently of the nature of the biomass, were improved when the presence of the biomass was higher.Therefore, results here presented prove the potential of valorisation of microalgae consortia used in the effective treatment of wastewater through the development of bioplastic materials.

Sustainable Iron Recovery and Biodiesel Yield by Acid-Adapted Microalgae, Desmodesmus sp. MAS1 and Heterochlorella sp. MAS3, Grown in Synthetic Acid Mine Drainage.

Sustainable resource recovery is the key to manage the overburden of various waste entities of mining practices. The present study demonstrates for the first time a novel approach for iron recovery and biodiesel yield from two acid-adapted microalgae, Desmodesmus sp. MAS1 and Heterochlorella sp. MAS3, grown in synthetic acid mine drainage (SAMD). Virtually, there was no difference in the growth of the strain MAS3 both in Bold’s basal medium (control) and SAMD. Using the IC50 level (200 mg L–1) and a lower concentration (50 mg L–1) of iron in SAMD, the cell granularity, exopolysaccharide (EPS) secretion, iron recovery, and biodiesel were assessed in both the strains. Both cell granularity and accumulation of EPS were significantly altered under metal stress in SAMD, resulting in an increase in total accumulation of iron. Growth of the microalgal strains in SAMD yielded 12–20% biodiesel, with no traces of heavy metals, from the biomass. The entire amount of iron, accumulated intracellularly, was recovered in the residual biomass. Our results on the ability of the acid-adapted microalgal strains in iron recovery and yield of biodiesel when grown in SAMD indicate that they could be the potential candidates for use in bioremediation of extreme habitats like AMD.

Life cycle assessment of biofuel production from microalgae cultivated in anaerobic digested wastewater

The whole process of biofuel production from Desmodesmus sp. EJ 8-10 cultivated in anaerobic digested wastewater (ADW) under the optimal temperature was evaluated by using the method of Life Cycle Assessment (LCA). The energy efficiency and environment emissions were under considerable for the corresponding parametric study. The functional unit was 1 kg microalgae. It was concluded that the harvest stage was responsible for the main energy consumption during the microalgal whole pyrolysis process. The energy conversion efficiency of the whole process was larger than 1, which indicated that the process was profitable. The environmental impact of the whole process was 1165.67 mPET2000, among which the primary impact on the environment was eutrophication that accounts for 57.36%, followed by photochemical ozone synthesis (22.56%), acidification (17.36%); and global warming (2.73%), respectively. Keywords: microalgae, fast pyrolysis, life cycle assessment (LCA), anaerobic digested wastewater (ADW), biofuel production DOI: 10.25165/j.ijabe.20201301.4178 Citation: Li G, Lu Z T, Zhang J, Li H, Zhou Y G, Zayan A M I, et al. Life cycle assessment of biofuel production from microalgae cultivated in anaerobic digested wastewater. Int J Agric & Biol Eng, 2020; 13(1): 241–246.

Modeling biomass production during progressive nitrogen starvation by North Swedish green microalgae

Five newly isolated green algal species from Northern Sweden and one culture collection strain were tested for their ability to remove nitrogen and accumulate carbohydrates and neutral lipids (TAGs) under progressive nitrogen starvation. All six microalgal species increased biomass during N starvation, the amount of proteins decreased, and species dependent either TAGs and/or carbohydrates accumulated. Biomass of the algal strains Coelastrella sp. 3-4, Scenedesmus sp. B2-2 and S. obliquus RISE (UTEX 417) had very low final TAG content (≤3.4%) and high carbohydrate content (>41%) at the end of the starvation period. C. astroideum RW10 accumulated 9.2% TAGs and 53.9% carbohydrates during N-starvation; due to its modest growth rate (1.60 g/L and 1.06 1/day) resulting in low final biomass concentration, its cumulativeTAG and carbohydrate productivity were poor (175 mgTAG/system and 1.03 gCARBS/system). C. vulgaris 13-1 preferentially accumulated TAGs (10.3%) over carbohydrates (35%), with low minimal and maximal N quotas (2.27 and 11.6 mM/gDW) in its biomass and a very high growth rate (1.86 1/day) and cumulative TAGs productivity (278 mgTAG/system). Desmodesmus sp. RUC2 had the highest final biomass concentration (3.48 g/L) as well as cumulative TAG and carbohydrate productivity (269 mgTAG/system and 1.79 gCARBS/system). This species had the lowest minimal and maximal N quotas (1.58 and 8.50 mM/gDW) of all tested species, it can produce high amounts of biomass even when the available nitrogen concentration is low.A Droop's mathematical model with four basic parameters was applied to interpret the experimental data on N assimilation and biomass production under N starvation. The model corresponded well to the experimental data and therefore can successfully be applied to predict biomass production and N assimilation in Nordic algal species.

Auxin and cytokinin synergism augmenting biomass and lipid production in microalgae Desmodesmus sp. JS07

Microalgae are considered as a promising resource for biodiesel. Nevertheless, their commercial exploitation necessitates considerable impetus towards the development of approaches for increased biomass and lipid production. The present work elucidates the impact of exogenously supplemented auxins, i.e., indole-3-acetic acid (IAA), indole-3-butyric acid (IBA) and indole-3-propionic acid (IPA) and cytokinins, i.e., benzylaminopurine (BAP) and thidiazuron (TDZ) on biomass, lipid content and fatty acid profile of Desmodesmus sp. JS07. Among auxins, IBA improved the biomass and lipid content up to 1.96 ± 0.11 g/L and 34.88 ± 3.87 %, respectively while BAP among cytokinins increased the biomass and lipid content up to 1.88 ± 0.061 g/L and 31.84 ± 1.33 % respectively. Further, the cumulative impact of IBA (10 mg/L) and BAP (5 mg/L) resulted in their synergistic effect by stimulating biomass and lipid content up to 2.34 ± 0.032 g/L and 42.43 ± 1.88 % respectively. Auxins stimulated the superoxide dismutase activity, and cytokinins increased the enzymes (catalase and ascorbate peroxidase), scavenging reactive oxidative species, thereby regulating ROS homeostasis in microalgae. A significant alteration in the fatty acid profile owing to the type and dosage of phytohormones was detected. Hence, the strategy employing phytohormones could prove to be a meaningful approach for biofuel production.

Nutrients removal from piggery wastewater coupled to lipid production by a newly isolated self-flocculating microalga Desmodesmus sp. PW1

A newly isolated microalgal strain, Desmodesmus sp. PW1, possessing not only high potential for removing nitrogen and phosphorous from piggery wastewater but excellent self-flocculating ability, was provided here. Strain PW1 grew well in diluted and undiluted piggery wastewater, and could effectively remove total nitrogen and total phosphorus with removal rates up to 90% and 70%, respectively. In the laboratory scale by 30-L photobioreactor, microalga also performed well in TN (65.3%) and TP (83.5%) removal. Strain PW1 cultivated in the stationary phase achieved high self-flocculating efficiency (>90%) in 2.5 h of settling; meanwhile, temperature and pH slightly influenced on the flocculation. The potential mechanism on self-flocculation was considered related to hydrophobic extracellular polymeric substances. Furthermore, the fatty acid compositions of PW1 were mainly hexadecanoic acid, oleic acid and linoleic acid. Taken together, Desmodesmus sp. PW1 was the promising candidate to overcome the microalgae harvesting problem in piggery wastewater treatment.

Life cycle assessment of biofuel production from microalgae cultivated in anaerobic digested wastewater

The whole process of biofuel production from Desmodesmus sp. EJ 8-10 cultivated in anaerobic digested wastewater (ADW) under the optimal temperature was evaluated by using the method of Life Cycle Assessment (LCA). The energy efficiency and environment emissions were under considerable for the corresponding parametric study. The functional unit was 1 kg microalgae. It was concluded that the harvest stage was responsible for the main energy consumption during the microalgal whole pyrolysis process. The energy conversion efficiency of the whole process was larger than 1, which indicated that the process was profitable. The environmental impact of the whole process was 1165.67 mPET2000, among which the primary impact on the environment was eutrophication that accounts for 57.36%, followed by photochemical ozone synthesis (22.56%), acidification (17.36%); and global warming (2.73%), respectively. Keywords: microalgae, fast pyrolysis, life cycle assessment (LCA), anaerobic digested wastewater (ADW), biofuel production DOI: 10.25165/j.ijabe.20201301.4178 Citation: Li G, Lu Z T, Zhang J, Li H, Zhou Y G, Zayan A M I, et al. Life cycle assessment of biofuel production from microalgae cultivated in anaerobic digested wastewater. Int J Agric & Biol Eng, 2020; 13(1): 241–246.

Photoprotection capacity of microalgae improved by regulating the antenna size of light-harvesting complexes

The unicellular green microalga Desmodesmus sp. S1 can produce total lipid over 50% of cell dry weight. A mutant D90G-19 induced by 12C6+ heavy ion irradiation generates more lipid which is 20% higher than its wild type (WT) under high light. The gene expression profiles in the photosynthetic pathway between the Desmodesmus sp. S1 WT and D90G-19 were compared, and several key genes were verified using qRT-PCR and western blotting. The psbA and psbD encoding the D1 and D2 subunits of PSII in D90G-19 were upregulated and higher than WT under high light, while an LHCB gene of Desmodesmus sp. was downregulated dramatically. The expression level of LHCB of D90G-19 was less than that of WT. The improved photoprotection capacity of D90G-19 was attributed to LHCII antennae probably due to the mutation of LHCB gene, which led to less photon into the electron transport chain. Furthermore, LHCBM, a homologous gene of LHCB in model microalgae N. gaditana Cas9+ strain, was knocked out using CRISPR/Cas9. The resulting mutant NgCas9-LHCBM showed an improved capacity to protect the photosynthetic complexes by dissipating extra light energy through non-photochemical quenching pathway. Therefore, the photoprotection capacity of microalgae can be improved by engineering the quantity of PSII subunits to fine-tune PSII reaction centers and the adjacent LHCII antennae.

A Feasibility Study of Wastewater Treatment Using Domestic Microalgae and Analysis of Biomass for Potential Applications

Water scarcity and emerging demands for renewable energy have increased concerns about energy security and advanced wastewater treatment, and microalgae have emerged as promising candidates to solve these problems. This study assesses the feasibility of microalgal wastewater treatment, and the utilization of the resulting microalgal biomass, as a renewable energy source. We cultured four selected microalgal species in filtered wastewater collected from the municipal treatment facility in Daegu, Republic of Korea. We measured nutrient consumption, growth rate, and physicochemical properties during cultivation, then analyzed the biomass for biochemical composition, ultimate analysis, proximate analysis, and biodiesel and lubricant properties, to estimate its potential applications. Desmodesmus sp. KNUA024 emerged as the most promising strain, removing 99.10% of ammonia nitrogen, 91.31% of total nitrogen, and 95.67% of total phosphate. Its biomass had a calorific value of 19.5 MJ kg−1, similar to terrestrial plants. α-linolenic acid was the most abundant polyunsaturated fatty acid (PUFA; 54.83%). Due to its PUFA content, Desmodesmus sp. KNUA024 also had a high iodine value, indicating its potential for use as a bio-lubricant. Therefore, Desmodesmus sp. KNUA024 shows promise for wastewater treatment, energy, and industrial applications.

Growth and primary cell composition of plateau microalgae Desmodesmus sp. QL96 under low temperature

Microalgae Desmodesmus sp. QL96 was newly isolated from Northwest Tibetan Plateau area which featured low temperature and oxygen content. In this work, Desmodesmus sp. QL96 was cultivated at 4 °C, and the algal growth and cell composition was investigated. It turned out that the microalgae has stayed at lag phase for over 10 days post inoculation, with a slight increase in cell numbers in the following 18 days. The cell content composed mainly of proteins with a percent of more than 40%, followed by lipid, though their amount varying over the culture time. The adaptation of this microalgae to extreme environmental condition deserves a further study.

Organic degrading bacteria and nitrifying bacteria stimulate the nutrient removal and biomass accumulation in microalgae-based system from piggery digestate

The microalgae-based system has been applied in anaerobic digestate treatment for nutrient removal and biomass production. To optimize its performance in treating piggery digestate, here, commercial bacterial agents, including organic degrading bacteria (Cb) and nitrifying bacteria (Nb), were inoculated into the microalgae-based system dominated by Desmodesmus sp. CHX1 (D). Reactor DN (inoculated with D and Nb) and DCN (inoculated with D, and Cb to Nb at a ratio of 1:2) have better performance on NH4+-N removal, with a final efficiency at 40.26% and 39.87%, respectively, and no NO3−-N or NO2−-N accumulations. The final total chlorophyll concentration, an indicator of microalgal growth, reached 4.74 and 5.47 mg/L in DN and DCN, respectively, three times more than that in D. These results suggested that high NH4+-N removal was achieved by the assimilation into high microalgal biomass after the inoculation with functional bacteria. High-throughput sequencing showed that the richness of microbial community decreased but the evenness increased by inoculating functional microorganisms. Microalgae aggregating bacteria were Cellvibrio, Sphingobacterium, Flavobacterium, Comamonas, Microbacterium, Dyadobacter, and Paenibacillus. This study revealed that the inoculation with functional bacteria reconstructed the microbial community which benefited for the microalgal growth and nutrient removal, providing a promising strategy for treating highly-concentrated digestate.

Isolation, screening and comprehensive characterization of candidate microalgae for biofuel feedstock production and dairy effluent treatment: A sustainable approach

In this study, the indigenous native microalgae were isolated from domestic and dairy effluent (DE) and further screened for DE treatment and lipid accumulation. All the isolated microalgae were examined for their growth adaptability in DE. The growth parameters of 15 isolates were determined and the following six isolates further selected for comprehensive analysis and identified as Desmodesmus sp. ASK01, Chlorella sp. ASK14, Scenedesmus sp. ASK16, Scenedesmus sp. ASK22, Chlorella sp. ASK25 and Chlorella sp. ASK27. The nutrient remediation capacity of six isolates as well as its lipid accumulation potential and biomass composition were determined. The Scenedesmus sp. ASK22 showed the best combined results and promising strain for the DE treatment and biofuel production. Biomass composition of Scenedesmus sp. ASK22 showed an oil accumulation of 30.7% (w/w) and biomass yield 1.22 g L−1. The fatty acid methyl ester (FAME) mainly composed of C15:0, C16:0, C18:0, C18:1 and C18:3.

Exploring biostimulation of plant hormones and nitrate supplement to effectively enhance biomass growth and lutein production with thermo-tolerant Desmodesmus sp. F51

In this study, the interactive effect of plant hormone-salicylic acid and succinic acid on biomass growth, lutein content, and productivity of Desmodesmus sp. F51 were investigated. The results demonstrated that the synergistic action of salicylic acid and succinic acid could effectively enhance the assimilation of nitrate and significantly improve lutein production. The maximal lutein content 7.01 mg/g and productivity 5.11 mg/L/d could be obtained with a supplement of 100 µM salicylic acid and 2.5 mM succinic acid in batch culture. Furthermore, operation strategy of nitrate fed-batch coupled with supplementation for succinic acid and salicylic acid resulted in further enhancement of lutein content and productivity by 7.50 mg/g and 5.78 mg/L/d, respectively. The performance is better than most of the previously reported values.

A novel intracellular synthesis of silver nanoparticles using Desmodesmus sp. (Scenedesmaceae): different methods of pigment change

The present study describes the role of cellular pigments in the biosynthesis of silver nanoparticles. The use of algae for nanoparticle synthesis has advantages such as being fast, eco-friendly, biocompatible, and non-toxic chemicals. However, it takes place in a shorter time and with lower cost than other biosynthesis methods. In this study, we synthesized silver nanoparticle intracellularly from 5 mM AgNO3 solution-mediated Desmodesmus sp. as reducing agent. The successful synthesis of silver nanoparticles was confirmed by UV–Vis, TEM, XRD and confocal analysis. It was observed that the algal cells synthesized under TEM analysis are intact and the nanoparticles accumulate in the compact inner region of the cells without forming aggregates. In the UV–Vis spectroscopy analysis, nanoparticle synthesis was performed in the first 24 h, which was confirmed by the reduction of chlorophyll content. In addition, this situation was seen in confocal microscopy analysis due to the autofluorescence of the Desmodesmus sp.

Autochthonous microalgae cultivation with anaerobic effluent: isolation of strains, survivorship, and characterization of the produced biomass

Six Chlorophyta strains were isolated from the effluent of an anaerobic reactor treating municipal wastewater and identified as Desmodesmus sp. L02, Chlorococcum sp. L04, Coccomyxa sp. L05, Chlorella sp. L06, Scenedesmus sp. L08 and Tetradesmus sp. L09. The microalgae strains were cultivated in unsterilized wastewater under laboratory conditions to determine their potential to survive under non-sterile conditions. The strains were also cultivated in sterilized wastewater in order to analyze their nutrient removal potential and characterize the produced biomass. Amongst the isolated microalgae, Chlorella sp. L06 had the highest survivorship percentage (90%) for ten days of culture, whilst Desmodesmus sp. L02 had the lowest, not exceeding 1.8% after 24h of inoculation. The dried biomass of the isolates showed an average of 28.7% of protein, 15.4% of lipids and 14.8% of carbohydrates, with Chlorococcum sp. L04 reaching 29.3% of carbohydrates. In terms of nutrients, nitrogen removal varied from 59.2 to 93%, and phosphorus removal ranged from 79.1 to 95.4%, with Tetradesmus sp. L09 being the most efficient strain.

Comparative transcriptome analysis of wild type and an oleaginous mutant strain of Desmodesmus sp. reveals a unique reprogramming of lipid metabolism under high light

A mutant generated via ethylmethane sulfonate mutagenesis, Desmodesmus sp. G3, exhibited greater biomass and neutral lipid production over the wild type (WT) strain Desmodesmus sp. G41 in our previous study (Zhang et al., Bioresour Technol 207:268–275, 2016). G3 possessed a higher growth rate and lipid production than WT, with a biomass yield and total lipid content of 1302.86 mg L−1 and 48.58% respectively, which was promoted by 20.50% and 18.84%, compared to WT. Comparative transcriptome analysis was performed to elucidate the mechanism supporting enhanced biomass and lipid production in G3. A total of 1488 differentially expressed genes (DEGs) was identified comparing G3 and WT sequencing datasets, of which 753 and 735 genes were upregulated and downregulated respectively in G3. Pathway enrichment analysis indicated that ‘photosynthesis,’ ‘starch and sucrose metabolism,’ ‘fatty acid elongation,’ and ‘pyruvate metabolism’ were the notable represented DEGs-enriched pathways that might affect cell growth and lipid metabolism. Light harvesting capture was enhanced in G3. To protect PSII from photodamage, light harvesting complex-dependent non-photochemical quenching and state transitions was employed as the photoprotective strategy. De novo fatty acids (FAs) synthesis in chloroplast was downregulated in G3 while mitochondrion localized FAs elongation was enhanced to recycle carbon skeletons for lipid biosynthesis. Pyruvate mechanism was activated in G3 to generate acetyl-CoA through a pyruvate dehydrogenase bypass pathway, as the predominant pathway to provide precursor for lipids biosynthesis.

Effects of Copper and pH on the Growth and Physiology of Desmodesmus sp. AARLG074.

Copper (Cu) is a heavy metal that is widely used in industry and as such wastewater from mining or industrial operations can contain high levels of Cu. Some aquatic algal species can tolerate and bioaccumulate Cu and so could play a key role in bioremediating and recovering Cu from polluted waterways. One such species is the green alga Desmodesmus sp. AARLG074. The aim of this study was to determine how Desmodesmus is able to tolerate large alterations in its external Cu and pH environment. Specifically, we set out to measure the variations in the Cu removal efficiency, growth, ultrastructure, and cellular metabolite content in the algal cells that are associated with Cu exposure and acidity. The results showed that Desmodesmus could remove up to 80% of the copper presented in Jaworski’s medium after 30 min exposure. There was a decrease in the ability of Cu removal at pH 4 compared to pH 6 indicating both pH and Cu concentration affected the efficiency of Cu removal. Furthermore, Cu had an adverse effect on algal growth and caused ultrastructural changes. Metabolite fingerprinting (FT-IR and GC-MS) revealed that the polysaccharide and amino acid content were the main metabolites affected under acid and Cu exposure. Fructose, lactose and sorbose contents significantly decreased under both acidic and Cu conditions, whilst glycerol and melezitose contents significantly increased at pH 4. The pathway analysis showed that pH had the highest impact score on alanine, aspartate and glutamate metabolism whereas Cu had the highest impact on arginine and proline metabolism. Notably both Cu and pH had impact on glutathione and galactose metabolism.

An effective method for harvesting of microalga: Coculture-induced self-flocculation

Microalgae are potential candidates for the production of third-generation biofuels, but the high-energy consumption of harvesting biomass makes current commercial microalgal biodiesel production economically unfeasible. Self-flocculation is regarded as a cost-efficient strategy for harvesting microalgae. In this work, a coculture system was developed by the mixotrophic cultivation of two poorly flocculating microalgae, Desmodesmus sp. ZFY and Monoraphidium sp. QLY-1, for self-flocculation of microalgal cells. The flocculation efficiency for harvesting was enhanced to 85.33% with settling for 4 h in coculture, which was better than that in mono-culture (57.98% and 32.45%). Coculture resulted in changes in both the concentration and composition of extracellular polymeric substances (EPS) in the culture, which partially contributed to cell aggregation. The concentration of polysaccharides in LB-EPS ranged from 27.01% and 27.35% in mono-culture to 46.53% in coculture. Moreover, the fine properties of lipid productivity (93.99 mg L−1 d −1) and fatty acid composition in coculture indicated the potential to produce biodiesel within most biodiesel standards.

Improvement of Energy Network by Naturally Farming of Chlorophyll-bearing Algae: Effects of Culture Condition Changes for the Yield of Microalgae

In this study, basic cultivation experiments were performed on microalgae Desmodesmus sp, then, the experiment results were deductively expanded, and the use of paddy in the off-season for farmers is advocated. As a result of the continuous culture experiments using 100 mL test tubes, 101.3 mg dry biomass was harvested in the aeration culture using the BG-11 medium. In the aeration culture with mixing CO2, the maximum harvest was obtained under the 10%-CO2 concentration. Considering about CO2 concentration, the condition of 1%-CO2 was superior in CO2 use efficiency. Based on the changes in the pH of the medium, algae such as Desmodesmus sp exchanges ions between the inside of the cell and the surrounding environment, and changes the surrounding environment in order to adapt themselves. In the proforma calculation of second crops in paddy fields, 26.4 million tons dry biomass is harvested in 120 days long of culture a year. Considering that the harvested dry biomass amount, 187 × 106 GJ power energy is obtained by burning them. This amount of energy corresponds to about 5.2% of total electricity.